Summary Rationale: Cardiac resynchronisation therapy (CRT) with biventricular pacemakers and implantable cardiac defibrillators (ICD) has proven to be a valuable therapy in selected patients with systolic heart failure, ameliorating both morbidity and mortality. However, with current selection criteria and implant technique, about 20 to 30 % of patients remain non-responders. Non-responders might be due to failing selection criteria or methodology in casu echocardiography. Moreover, the definition of response to CRT is unequivocal and there is a need for a simple and reproducible measure of response with low inter- and intra-observer variability.